1. Field of the Invention
A method utilized in a wireless communication and related communication device are disclosed, and more particularly, to a method of handling minimization of drive tests in radio access technology change in a wireless communication system and related communication device.
2. Description of the Prior Art
Coverage is something that a customer can easily notice through the terminal user interface (UI) (i.e. out-of-service area indication), and is a major criteria that a customer considers when comparing service provided by different operators. With the increase in data service provision, downlink throughput is also an important criterion by which many customers judge the performance of the network. Poor uplink coverage will impact user experience in terms of call setup failure/call drop/poor uplink voice quality.
Accordingly, it is very important for operators to be aware of the coverage/throughput their networks provide, and rigorous “drive tests” are performed to collect such information. However, what has to be taken account of is that the drive tests for network optimization purposes are costly and cause also additional CO2 emissions, so it is desirable to develop automated solutions, including involving UEs in the field, in 3GPP to reduce the operator costs for network deployment and operation. Therefore, minimization of drive tests (MDT) functionality involving measurement is performed or logged by UE to collect information (or called measurement logs) in idle mode or connected mode, to reduce network maintenance costs for operators, ensure faster optimization cycle resulting in higher customer satisfaction and nonetheless help to reduce the carbon emission to protect the environment.
Note that, when a UE with MDT functionality receives a MDT measurement configuration message from a network (e.g. Universal Terrestrial Radio Access Network (UTRAN) in Universal Mobile Telecommunications System (UMTS), or Evolved Universal Terrestrial Radio Access Network (E-UTRAN) in Long-Term Evolution (LTE)), the UE shall perform measurement logging for the purpose of MDT and simultaneously start a timer for MDT measurement logging according to the MDT measurement configuration. In addition, the UE stops the MDT measurement logging only when the timer expires.
On the other hand, inter-radio access technology (inter-RAT) mobility involves transfer of a connection or mobility between a UE and a network from one RAT to another RAT. Inter-RAT procedure may occur due to handover, redirection, cell change order, cell selection or cell reselection. In the case of the cell reselection, the UE reselects a cell between cells using different RATs, such as GSM (Global System for Mobile communications)/GPRS (Global Packet Radio Service), UMTS and LTE.
However, the applicant notices that a UE may encounter problems associated to MDT measurement logging in RAT change as below based on a direct image on a basis of the prior art UMTS or LTE system.
In the first scenario, based on the 3GPP specification R2-105880, when a UE in UMTS system receives the MDT LOGGING CONFIGURATION message from the UTRAN, the UE performs MDT measurement logging in an idle mode, CELL_PCH or URA_PCH state and simultaneously starts the timer T326 for the MDT measurement logging. On the other hand, according to the 3GPP specification TS 25.331, when the UE performs inter-RAT procedure (e.g. inter-RAT cell selection/reselection from a UTRAN, inter-RAT handover from UTRAN or inter-RAT cell change order from UTRAN), and has successive in reselecting a cell in the target RAT (e.g. Global System for Mobile Communications (GSM)/GPRS or Evolved Universal Terrestrial Radio Access Network (E-UTRAN)), the UE releases all UTRAN specific resources. Therefore, the UE stops the timer T326 since this timer is associated to UTRAN specific resource. This results in that the UE keeps MDT measurement configuration and thereby logging endlessly. The UE power and storage are drained due to endless logging.
In the second scenario, based on the 3GPP specification R2-105879, when a UE in LTE system receives the IdleLoggingConfiguration message from E-UTRAN, the UE performs MDT measurement logging in radio resource control (RRC) idle mode and simultaneously starts timer T330 for MDT measurement logging. In addition, when the UE performs inter-RAT procedure from E-UTRAN to UTRAN, GERAN or CDMA 2000, the UE releases all EUTRAN specific resources according to the prior art. Therefore, the UE stops the timer T330 since this timer is associated to E-UTRAN specific resource. This results in that the UE keeps MDT measurement configuration and thereby logging endlessly. The UE power and storage are drained due to endless logging.